Things just got a lot worse for users of the Sony PlayStation Network.

With the service still offline after almost six days, Sony has now said that an intruder stole personal information about its users, potentially including their credit card numbers.

"We have discovered that between April 17 and April 19, 2011, certain PlayStation Network and Qriocity service user account information was compromised in connection with an illegal and unauthorized intrusion into our network," Sony said in a blog post Tuesday.

It was still investigating the matter, but believes that the intruder obtained names and addresses for registered PlayStation Network and Qriocity users, along with their birthdates, e-mail addresses and other personal information.

"While there is no evidence at this time that credit card data was taken, we cannot rule out the possibility," Sony said. "If you have provided your credit card data through PlayStation Network or Qriocity, out of an abundance of caution we are advising you that your credit card number (excluding security code) and expiration date may have been obtained."

Sony now advises users to "remain vigilant" and be on the lookout for e-mail, telephone and postal scams. Hackers will sometimes use personal data they have stolen to target users with phishing attacks or try to trick them into handing over further data.

"Sony will not contact you in any way, including by email, asking for your credit card number, social security number or other personally identifiable information," the company said. "If you are asked for this information, you can be confident Sony is not the entity asking."

When the services come back up, users should change their logins and passwords, which Sony said were also stolen.